Mammo-50: Reduced mammogram frequency postsurgery may suffice for older women

Breast cancer survivors who are at least 50 years of age appear to do well with less frequent mammographic surveillance, with survival outcomes being no worse than with annual mammograms, according to data from the phase III Mammo-50 trial.

Breast cancer-specific survival (BCSS) at 5 years was 98.3 percent (95 percent confidence interval [CI], 97.7–98.8%) in the less frequent arm versus 98.2 percent (95 percent CI, 97.5–98.6) in the annual arm (hazard ratio [HR], 0.92, 95 percent CI, 0.64–1.32). Less frequent mammographic surveillance demonstrated noninferiority at 3-percent margin (p<0.0001) and 1-percent margin (p=0.003). [SABCS 2023, abstract GS03-02]

Results for recurrence-free interval (RFI) and overall survival (OS) followed the same pattern. Five-year RFI rate was 94.1 percent in the less frequent arm versus 94.1 percent in the annual arm (HR, 1.00, 95 percent CI, 0.81–1.24; noninferiority at 2-percent margin, p=0.006). Five-year OS was 94.5 percent versus 94.7 percent (HR, 1.08, 95 percent CI, 0.87–1.33; noninferiority at 2-percent margin, p=0.008), respectively.

These findings, according to lead study author Dr Janet Dunn of University of Warwick in Coventry, England, UK, provide evidence for altering current clinical practice regarding post-treatment breast cancer surveillance.

Mammo-50 challenges the recommendation of annual mammographic surveillance for an unspecified period after treatment for early breast cancer that is prevalent in the US and Europe. Annual mammograms pose a significant cost burden to the healthcare system and cause distress to the patients, Dunn noted. As such, a less-frequent surveillance approach could potentially alleviate the financial strain on healthcare systems and reduce patient anxiety. [CA Cancer J Clin 2016;66:43-73; Ann Oncol 2019;30:1194-1220; Psychosom Med 2004;66:104-112; J Clin Nurs 2012;21:3223-3234]

Distress thermometer

A total of 15,967 mammograms had been performed in the annual arm and 8,662 in the less frequent arm. Rates of compliance to the mammographic surveillance schedule were 83 percent and 69 percent, respectively. However, Dunn pointed out that compliance was affected by the COVID-19 pandemic, with roughly 35 percent of women missing their mammograms during the pandemic.

Nevertheless, a sensitivity analysis that included 76 percent of the women who fully complied with their scheduled mammograms as per protocol consistently established the noninferiority of the less frequent surveillance for BCSS, RFI, and OS.

“An important part of the study … was the distress thermometer,” and 6 percent of women indicated reported experiencing a high level of anxiety of distress prior to randomization, Dunn said.

The high level of distress remained at 6 percent to 10 percent throughout the follow-up, with no differences between the arms. Such level of distress was largely driven by fatigue (58 percent), sleep problems (54 percent), worry/fear/anxiety (50 percent), hot flushes (41 percent), memory or concentration problems (39 percent), pain (38 percent), and sadness/depression (35 percent).

Clearly, there is a need for ongoing survivorship support, according to Dunn. She called for a streamlined process that allows women to access resources and support for managing their distress.

Study details

Mammo-50 included 5,235 women who were at least 50 years of age at the initial diagnosis of breast cancer (invasive or ductal carcinoma in situ) and were free of recurrence 3 years after curative surgery. These women were randomly assigned to undergo annual or less frequent mammograms. In the less frequent arm, women who had had a wide local excision underwent biannual mammograms, while those who had had a mastectomy underwent mammograms at a 3-year interval.

Of the women, 83 percent were aged 55–75 years, 80 percent had undergone conservation surgery, 87 percent had invasive disease, 22 percent had node-positive disease, 83 percent had oestrogen receptor-positive tumours, and 73 percent were taking hormone therapy at the time of randomization. Patient characteristics were balanced across arms.

Over a median follow-up of 5.4 years or 8.7 years after curative surgery, 319 women died, including 104 of breast cancer (51 in the less frequent arm and 53 in the annual arm). A new invasive breast cancer event occurred in 156 women in the less frequent arm and 164 in the annual arm (55 loco-regional recurrences, 85 new breast primaries, 139 distant recurrences, and 41 with multiple invasive events).

Dunn shared that she and her team will perform further analysis on women that had a recurrence, wherein they will look at the timing and types of recurrence and link these to any prognostic risk at baseline.